I. Field of the Invention
The present invention relates generally to electronic monitoring systems and, particularly, to a monitoring system which monitors the status of a plurality of remote stations.
II. Description of the Prior Art
Hotels and similar institutions are plagued by the theft of expensive appliances, such as television sets, from the hotel room. There have been a number of previously known devices to minimize the theft of such appliances from the hotel room but none of these previously known devices have proven wholly effective in operation.
In one previously known device, one end of a resistor is secured to an electrical ground in the appliance while the other end of the resistor is electrically connected by a wire to a main station. At the main station, the resistor in the appliance forms a part of an electrical bridge, such as a Wheatstone brige, so that any tampering with the resistor sensor such, as would occur if the wire were cut, upsets the balance of the electric bridge. An indicator light at the main station is then activated once the bridge balance and has been upset to alert the operator of the possible theft of the appliance.
These previously known devices, however, suffer from a number of disadvantages. First, a skilled thief can tamper with the sensor to maintain the resistance of the sensor the same and permit the removal of the appliance without setting off the alarm. A still further disadvantage of these previously known devices is that each sensor requires a separate indicator light at the main station so that, for large hotels, the main station control panel is not only large and unsightly in appearance but also expensive in construction.
Another common problem with hotels and similar institutions is that newly enacted regulations often require the hotel to place a smoke detector alarm in each hotel room. The previously known systems would require the installation of a system completely separate from the appliance antitheft system.
A further problem associated with hotels and similar institutions are burglary of other property from hotel rooms in which the lawful occupants are not present. There are no systems known to the applicant for monitoring the hotel rooms against unexpected and unlawful entry into the hotel room.